The lower limb functions as an integrated unit during activity, and in a healthy lower limb the hip, knee, ankles, toes and the muscles, ligaments and other dynamic functional parts of the lower limb act as a closed kinetic chain. To return an injured joint to its previous level of performance it must also perform as an integrated unit in positions of function while undergoing rehabilitation. Isolated testing and rehabilitation address only the isolated injured joint, while the progressive functional integration of that joint may be even more important than its isolated condition.
In order to analyze the rehabilitation of a healing lower extremity joint analysis of the weight distribution of which the foot is capable of attaining is significant, and devices have been proposed for such purpose as shown in U.S. Pat. Nos. 2,095,268 and 4,014,398. Exercise devices for the ankle and lower leg are known as shown in U.S. Pat. No. 4,635,932, and it is known to use computerized analysis systems for analyzing and recording forces acting on the human foot, such as shown in U.S. Pat. No. 4,452,447. However, previously known devices are not of such sophistication and construction as to provide both functional closed-chain assessment and rehabilitation of the lower limb and produce objective data regarding the functional performance of the lower extremity.
A widely recognized method of closed-chain dynamic rehabilitation for the lower extremity is the Biomechanical Ankle Platform System (BAPS), and this device permits rehabilitation of the lower limb as a unit wherein the lower extremity is able to repair itself in a functional, integrated manner. The BAPS system is described in U.S. Pat. No. 4,653,748, and the foot support disc disclosed in this patent also appears in U.S. Pat. No. Des. 278,924.
It is an object of the invention to provide a biomechanical analysis system for the lower extremity which permits functional closed-chain assessment and rehabilitation, and complete readily analyzable data is instantly produced which permits rapid evaluation.
A further object of the invention is to provide a method for biomechanical analysis of the lower limb wherein the method is based on the principles of dynamic closed chain rehabilitation used with the BAPS system and wherein rapid assessment of the condition of the lower extremity is possible and objective data instantaneously obtained with respect to the analysis.
Yet another object of the invention is to provide a method for biomechanical analysis of the lower extremity capable of analyzing the functioning of the lower extremity as a integrated unit while simultaneously undergoing rehibilitation.
An additional object of the invention is to provide a biomechanical analysis system for the lower extremity wherein an electronic assessment output is achieved with the use of the apparatus and an instant analysis of the functional performance of the extremity is provided and the patient may view this performancy on a display screen permitting an immediate visualization of the state of progress and quantitative analysis.
Another object of the invention is to provide a biomechanical apparatus for the lower extremity which is easily usable by the relatively unskilled operator, is easily used by the patient, and is adjustable though a wide range of operating characteristics to permit immediate analysis by the patient of his progress.
In the practice of the inventive concepts apparatus is employed which permits visual and recordable evaluation of the exercising and rehabilitation when utilizing the BAPS system for lower extremity rehabilitation. The invention contemplates a method of lower extremity biomechanical analysis which is immediate and complete and permits immediate analysis and recognition of various lower extremity conditions such as equinas, supinatory and pronatory foot conditions, and permits analysis of pressures of which the lower limb is capable of exerting anterolaterally, anteromedially, posterolaterally and posteromedially and the flexibility of the lower limb and ankle may be immediately analyzed, for instance, a lack of dorsiflexion may be immediately discerned. The apparatus permits a more definitive assessment of the lower extremity than was heretofore available, and with the use of the invention a more explicit therapy program can be devised which is more efficient than previously achievable.
The apparatus of the biomechanical analysis system of the invention includes a frame of a generally rectangularly configuration having patient hand rails and supports vertically extending thereabove. A weight sensing platform is mounted upon the frame supported upon a plurality of accurate, spaced weight measuring sensors whereby the sensors are capable of accurately determining the presence of weight as applied to the platform at a given location and produce a proportional electrical signal.
A vertically extending shaft passes through the platform without connection thereto, and the upper end of the shaft is provided with universal joint structure for supporting a foot support disc having a peripheral configuration similar to that shown in U.S. Pat. No. 4,653,748. This disc includes a configured periphery as described in the aforementioned patent, and the patient places one foot upon the disc while grasping the hand holding means above the platform.
The universal joint support of the disc permits the patient to nutate the disc about its periphery and apply weight to the platform through the disc outer periphery at various distances from the shaft axis as determined by the disc configuration. The upper surface of the platform includes a plurality of switches sensitive to engagement by the disc periphery wherein the angular point of engagement of the disc periphery on the platform may be accurately electronically determined. Accordingly, by the use of the disc operated switches and the platform weight sensors the amount of weight exerted by the patient through the disc upon the platform may be very accurately located and determined.
The electronic output generated by the platform sensors and the switches is fed into a computerized system having a software program capable of analyzing the input and producing an output to a cathode ray tube (CRT) monitor permitting an immediate visual observation of the results of the disc movement and weight imposed upon the disc and platform. This analysis permits various lower limb conditions to be immediately ascertained, and the program, when using a color monitor, permits various shades of color to become visible, the color being proportionate to the amount of weight being applied to the platform at various angular positions relative to the shaft axis.
The shaft is supported upon elevator structure which permits the shaft to be raised and lowered relative to the platform which will change the angle of operation of the foot supporting disc, i.e. the higher the disc is above the platform the greater the angle of disc displacement required to engage the disc periphery with the platform upper surface. Thus, in initial stages of rehabilitation the foot supporting disc may be located relatively close to the platform minimizing the flexing of the ankle and lower extremity required to engage the disc periphery with the platform. As rehabilitation progresses, the shaft and disc may be raised further from the platform to increase the extent of ankle movement required.
The computerized analysis and output permits instantaneous visualization of the operation of the biomechanical analysis system and, of course, by the use of internal memory or use of a printer a copy of each patient's testing may be readily retained for comparison with subsequent testing. Depending on whether the nutation of the foot supporting disc is to be achieved primarily by ankle movement, or by movement of substantially the whole lower leg or extremity a wide variety of conditions of the lower extremity may be readily observed and analyzed, and the practice of the invention permits complete assessment of the function of the lower extremity and the patient can be actively involved in his own rehabilitation and can realize his progress as it occurs. A further advantage of the invention results from the documentation achievable with the invention with respect to insurance claims.